Identifying Key Stressors Driving Biological Impairment in Freshwater Streams in the Chesapeake Bay Watershed, USA

Abstract

Biological communities in freshwater streams are often impaired by multiple stressors (e.g., flow or water quality) originating from anthropogenic activities such as urbanization, agriculture, or energy extraction. Restoration efforts in the Chesapeake Bay watershed, USA seek to improve biological conditions in 10% of freshwater tributaries and to protect the biological integrity of existing healthy watersheds. To achieve these goals, resource managers need to better understand which stressors are most likely driving biological impairment. Our study addressed this knowledge gap through two approaches: 1) reviewing and synthesizing published multi-stressor studies, and 2) examining 303(d) listed impairments linked to biological impairment as identified by jurisdiction regulatory agencies (the states within the watershed and the District of Columbia). Results identified geomorphology (i.e., physical habitat), salinity, and toxic contaminants as important for explaining variability in benthic community metrics in the literature review. Geomorphology (i.e., physical habitat and sediment), salinity, and nutrients were the most reported stressors in the jurisdictional impairment analysis. Salinity is likely a major stressor in urban and mining settings, whereas geomorphology was commonly reported in agricultural settings. Toxic contaminants, such as pesticides, were rarely measured; more research is needed to quantify the extent of their effects in the region. Flow alteration was also highlighted as an important urban stressor in the literature review but was rarely measured in the literature or reported by jurisdictions as a cause of impairment. These results can be used to prioritize stressor monitoring by managers, and to improve stressor identification methods for identifying causes of biological impairment.

Individual and combined impacts of carbon dioxide enrichment, heatwaves, flow velocity variability, and fine sediment deposition on stream invertebrate communities

“…Loads of fine sediment (commonly defined as particles <2 mm) exceeding natural variability due to land‐use activities, and most commonly associated with intensive agricultural practices (Wood & Armitage, 1997), are a pervasive stressor frequently linked to biological change in running freshwaters (Fanelli et al., 2022; Kemp et al., 2011; Vörösmarty et al., 2010). Sediment settling on a stony‐bottomed streambed fills interstitial spaces, resulting in reduction of habitat for many benthic invertebrates, while benefitting those that utilize fine sediment (Lenat et al., 1981), for example, by burrowing or constructing casings (Dudgeon, 1994).…”

Nature-Based Solutions in Spatial Planning: How to Adapt Land Use to Natural Heterogeneity in Agroforest Landscapes in Russia

“…Phase J-Which Anthropogenic Loads and Configuration Are Admissible? (Steps 34-36) Phase K. Which technologies are the most ecologically and economically effective within the limits of land use units (steps [37][38].…”

“…The particular definition of a buffer zone is a geochemical barrier that is a site where matter flows slow down sharply and certain chemical elements accumulate due to contrasts in geochemical condition or biological absorption [27,36]. The argument that a location's priority is based not only on its own characteristics but on those of other locations as well [37] is significant for both nature conservation and land use planning. Spatial context provides rationales for relating the spatial proportions, rareness, and typicality of landscape units to their socio-economic and ecological values [20,38].…”

Teasing out the Effects of Natural Stressors at Chemically Contaminated Sites

“…The multitude of stressors present within aquatic systems, often introduced by anthropogenic activity, have emphasized the importance of stressor characterization within these complex, dynamic environments. In the presence of multiple stressors, attribution of impairments to their respective stressor can be a challenging process (Fanelli et al, 2022). Establishing a causal link between stressors and observed ecological impairments is a critical component of contaminated site assessment; formulation of plans for remediation and restoration depend on proper diagnosis of the problem (Burton & Johnston, 2010).…”

“…The presence of toxic contaminants in waterways and sediments is a well‐documented stressor category within risk assessments (Fanelli et al, 2022). A common approach in assessment of sites suspected to be compromised by the presence of one or more pollutants is to compare detected concentrations of samples with established sediment and water quality guidelines (Altenburger et al, 2019; Blasco & Picó, 2009; Burton & Johnston, 2010).…”